Fluid heater

ABSTRACT

A swimming pool heater having an infrared gas burner therein for supplying radiant heat to pool water flowing in a tubular heat exchanger adjacent the burner plate. The heat exchanger is arranged in a heater housing to define therewith a flow path adjacent the tubes for the products of combustion from the burner whereby additional heat by convection is supplied to the tubes from the exhaust gases. The input end of the heat exchanger includes a valve member adapted to maintain a predetermined rate of flow of water through the tubes and to bypass excess water back to the pool.

United States Patent [72] Inventors Edward A. Reid, Jr.; 3,l 18,430 l/l964 Russellet al l22/250 Robert G. Venendall,bothof Columbus, 3,267,909 8/1966 McClanahan 122/250 Ohio 3,292,598 12/1966 Milleret al. l22/406 [21] AppLNo. 7,445 3,315,646 4/1967 Witten,.lr l22/367X [22] Filed Feb. 2, 1970 [451 be irzmi s'ssszaiizmxfis' [73] Assignee Columbia Gas System Service Corporation New York, N.Y.

ABSTRACT: A swimming ool heater havin an infrared as b h f l p d h g l fl g urnert erem or supp ying ra iant eat to poo water owing [54] in a tubular heat exchanger adjacent the burner plate. The aims rawmg heat exchanger is arranged in a heater housing to define [52] US. Cl 122/250 R, therewith a flow path adjacent the tubes for the products of l22/367 C, l22/406 R combustion from the burner whereby additional heat by con- [51] lnt.Cl F22b 27/08 vection is supplied to the tubes from the exhaust gases. The Field ofSearch 122/248, in ut end of the heat exchanger includes a valve member P 250,367,367 C, 406 adapted to maintain a predetermined rate of flow of water through the tubes and to bypass excess water back to the pool. [56] References Cited UNITED STATES PATENTS 2,987,259 6/1961 Lindquist l22/250R :54! l7 I I \c "=1 5O 92 I 3.5L as 4 crw---tz.---'-- 9o-\. s4 w 37 1r; I GZ f f" W l r, 7 I :'7 a 5": a: 3

hi 64 T "J'4 J 90 408 2 PATENTED UEC28 |97l SHEET 2 OF 4 Fig.2

INVENTOR. Edward A. Reid,Jr.

BY Robert G. Venendcol PATENTEDOE28I971 31630175 SHEET 3 0K4 ZIS' ZIZ 7 1 INVENTOR. P19. 7 Edward A. Reid,dr.

BY Robert G. Venendaal ATTORNEYS PATENIEU UEC28I97I 3,630,175

SHEET u [1F 4 9 INVENTQR.

Edward A. Re|d,J|'. BY Robert G. Venendool ATTORNEYS FLUID HEATER This invention relates to swimming pool heaters and more in particular to swimming pool heaters having infrared gas burners for supplying radiant heat to pool water.

. In swimming pool water treatment systems presently available, water is conducted from the pool through a filtering and circulation system and flow path for the water. Typically, these units utilize either direct blue flame gas burners, or an electrical heating element and they are relatively inefficient in the production of necessary heat. As a result, the cost of operation of conventional swimming pool heaters in order to maintain desirable water temperatures, particularly in large pools, is inordinately high.

It is an object of this invention to provide a heater unit for efficiently maintaining desired water temperatures in swimming pools. It is another object of this invention to supply increased amounts of heat to water in a swimming pool circulation system. It is a further object of the invention to provide a swimming pool heater wherein the volume of water flowing through the heater is controlled for maximum heat transfer efficiency. It is a still further object of this invention to provide compact, efficient and inexpensive swimming pool water heaters.

In accordance with an aspect of this invention a generally gastight housing is provided which contains a coiled heat exchange tube forming a part of the flow path in the swimming pool water pump and filtration system. A gas burner unit is mounted in the housing within the cylindrical chamber formed by the coiled heat exchange tube and the burner unit has an apertured peripheral sidewall forming a peripheral burner plate. A combustible gas mixture flows from the interior of the burner through these apertures for combustion therein, whereby the burner plate is heated to incandescence to produce radiant heat. This radiant heat is transmitted to the inside surface of the coiled heat exchange tube to heat water flowing therein, and, as will be more fully explained hereinafter, additional heat is transferred from the products of combustion to the coiled heat exchange tube by convection and conduction prior to discharge from the housing.

In another embodiment of the invention the gas burner is provided with an apertured base member or burner plate, similarly adapted to produce radiant heat. The heat exchanger in this embodiment includes a plurality of finned tubes interconnected to permit liquid flow therebetween and is positioned below the burner plate to receive infrared radiation from the burner plate. The heater is sealed so that all of the products of combustion flow between and around the tubes and provide additional heat by convection and conduction to the tubes and provide additional heat by convection and conduction to the tubes prior to discharge from the heater. Deflector baffles are provided below the heat exchange tubes and beneath the spaces between conduits to force the products of combustion passing through the heat exchanger to contact the entire surface area of the tubes to provide substantially uniform convective heat thereto. In addition, these deflector baffles reflect radiation which passes between the tubes back to the heat exchanger.

The burner plates of each embodiment are formed of a ceramic material having venturilike apertures or orifices as disclosed in commonly assigned copending Pat. Application Ser. No. 775,978, filed Oct. 2, 1968, the disclosure of which application is incorporated herein by reference. Flashback of flame through the orifices is prevented by the venturilike configurations which afford a throat portion of small cross section leading to an expanding or diverging outlet portion so that at least the requisite flow velocity is maintained within the throat portion for avoiding flashback over a relatively wide range of gas flow rates. Combustion of gases within the expanding portion of the orifices heats portions of the ceramic plate to incandescence to form radiant heat. By supplying the combustible gas to burners of this type at increased mass flow rates, as disclosed in commonly assigned copending U.S. Pat. application Ser. No. 3,943 filed Jan. 19, 1970 (identified by Curtis, Morris & Saffords File No. 17-1514), the disclosure of which application is also incorporated herein by reference, substantially the entire surface of the diverging outlet portion of each orifice is heated to incandescence and resulting in substantially great increases in the infrared output. In this manner a greater total heat output is achieved from the combustible gases supplied and a more efficient and compact water-heating unit results therefrom.

Pool water is supplied to the heaters of this invention through a control bypass valve which maintains the desired flow of water through the heat exchanger and bypasses any surplus water from the pool filtration system back to the pool.

The construction of such preferred embodiments as well as the advantages thereof will become further apparent from the following specification when considered in conjunction with the accompanying drawing wherein:

FIG. I is a perspective view of one embodiment of the swimming pool heater of the present invention showing the front and one side thereof;

FIG. 2 is a perspective view similar to FIG. 1 showing the rear and the other side of the heater;

FIG. 3 is a sectional view of the heater of FIG. 1, with parts broken away, taken on line 33 of FIG. 2;

FIG. 4 is a top plan view, with parts broken away of the device of FIG. I;

FIG. 5 is a perspective view similar to FIG. I of another embodiment of the invention;

FIG. 6 is a perspective view similar to FIG. 2 of the embodiment shown in FIG. 5;

FIG. 7 is a sectional view of the heater of FIG. 5; with parts broken away, taken on line 7-7 of FIG. 6;

FIG. 8 is a sectional view taken on line 8-8 of FIG. 7; and

FIG. 9 is a sectional view taken on line 9-9 of FIG. 7.

Referring now to the drawings and in particular to FIGS. 1 and 2, there is illustrated a swimming pool heater 10 constructed in accordance with the present invention. Heater 10 includes an outer decorative housing I2 having an upper portion 14 which is somewhat wider than its lower portion 16 and thus forms an overhang 17 for purposes which will be more fully explained hereinafter. A rear wall 18 of housing I2 includes a hinged door 19 which provides access to the interior of the housing and a pair of openings 20 and 22 through which water lines are connected to heater components within the housing. Water from the pools filter system is supplied by conduits (not shown) through opening 20 to the inlet 24 of manifold or header 26 and flows therefrom through one end 28 of a tubular heat exchanger 30 which is connected to the manifold.

Heat exchanger 30 is a generally tubular member formed of a close-packed cylindrical coil which surrounds an infrared heater or burner unit 32 which, as will be more fully described hereinafter, heats pool water flowing through the coil. The opposite end 34 of heat exchanger 30 is connected to manifold 26 adjacent its base, as seen in FIG. 3. The heater water flowing out of coil 30 into manifold 26 is discharged from manifold exhaust port 36 to a conduit (not shown), which extends through opening 22 in housing wall I8.

As seen in FIGS. 3 and 4, a valve 40 is positioned between manifold inlet 24 and end 28 of heat exchanger 30. Valve 40 controls the volume of water flowing into heat exchanger 30 and bypasses excess waterflow from the heater. The center portion of valve 40 includes conduit member 42 which is connected to manifold 26 at one end adjacent the heat exchanger inlet 28, and has its free end 46 extending into inlet 24. An annular valve member 48 is slidably mounted on conduit 42 and includes an annular sealing surface 50 adapted to engage a mating valve seat 52 on manifold 26 at inlet 24. Valve member 48 is biased against seat 52 by a spring 54 in order to close the annular opening between conduit 42 and inlet 24.

In pool water heaters it is desirable to maintain a constant flow of water through the heater coil to prevent excessive lime buildups within the coil, and valve 40 is provided to maintain this desired rate. Thus, the diameter of conduit 42 and the compression characteristics of spring 54 are chosen to permit only the maximum desired flow rate into the heat exchanger so that when the total water flow from the filtration system is equal to or below the desired flow rate through the heater coil all water flows through conduit 42, and through coil 30.

When the total waterflow rate from the filtration system increases above the desired flow rate through the heater, the additional force exerted by the increased flow of water against the tapered face 50 of valve member 48 moves it against the action of spring 54 away from its seat 52. Thus, the additional water flowing into the unit bypasses valve 40 and heater coil 30 and flows directly through header 26 to outlet 36 where it is mixed with heated water from coil 30 and returned to the swimming pool. Spring 54 is designed to maintain valve member 48 on its seat if the total waterflow rate from the filtration system is equal to or less than the desired flow rate through the heater coil.

Heat transfer coil 30 is positioned within a generally cylindrical housing 60 which is substantially gastight and enclosed by housing 12. Housing 60 is surrounded by thermal insulating material 62, as seen in FIG. 3, which prevents loss of heat from within the housing, as will be more fully explained hereinafter.

Heater unit 32 is positioned in housing 60 within the interior of the cylindrical space defined by coil 30 and includes upper and lower plate members 64 and a peripheral sidewall 66. Sidewall 66 is formed by eight apertured ceramic burner plates 68 to form an octagonally shaped burner, as seen in FIG. 4. Top plate 64 is connected to a supply duct 69 which extends through an opening 70 in top plate 72 of housing 60. A combustible mixture of gas and air is supplied to plenum chamber 67, in the interior of burner 32, defined by the ceramic plates 68, through duct 69 from gas supply line 74 and air blower 76. Gas supply line 74 may be provided with a conventional pressure regulator and electric gas valve (not shown) to volume accurately control the column of gas supplied to plenum 67. It is noted that rear wall 18 of housing 12 includes an opening 21 through which the gas supply line extends for connection to line 74. Air for blower 76 is drawn into housing 72 through a plurality of apertures 77 formed in the overhang portion 17 of the housing. By this construction unsightly flues and ducts are avoided and a compact structure is provided.

As shown in FIGS. 3 and 4, each of the apertures in burner plates 68 has a venturilike configuration which includes a throat portion 78 extending from an inlet 80 opening to plenum chamber 67 to an expanding or diverging outlet portion 82 at the outer face of the burner plate opposed to the interior surface of heat transfer coil 30. As disclosed in the above mentioned US. Pat. application Ser. No. 3,943 (C M & S File No. 17-1514) in burner plates of this type, with relatively high mass flow rates of supplied combustible fuel, a laminar flow is established in throat portion 78 which is projected into diverging outlet portion 82 as a central jet which separates from the surface of outlet portion 82 so as to create a zone of turbulent flow between the central jet and the surface of outlet portion 32. The lower velocity gases in this zone are ignited and these gases very efficiently transfer heat to the ceramic walls of the burner plates 68 at a temperature at which the ceramic material incandesces. In this manner the heat produced by a given area of burner plate is greatly increased and, as a result, the heater unit of the present invention may be made substantially smaller than other known swimming pool heater units. It is noted that in order to initially ignite the flowing gases, a spark or glow coil ignition system (not shown) is provided in the preferred embodiments in lieu of conventional pilot lights since the latter may readily be blown out under high winds when the heater is used for outdoor pools.

The incandescing burner plates 68 direct radiant heat toward coil 30 to heat the coil and thereby heat the water flowing therethrough. Additional heat is transferred to coil 30 from the products of combustion which are formed as a result of the combustion of gases in burner plates 68. This additional heat is supplied by convection and is facilitated by the tight or close-packed coil construction of heat exchanger 30, since the products of combustion are prevented from passing between individual helices of the coil and are thus forced upwardly in annular zone 86 between burner plates 68 and coil 30 and transfer a portion of their heat by convection thereto.

At the top 88 of housing 60 of the products of combustion flow, as indicated by the arrows in FIG. 3, over the top helical portion of coil 30 into the annular zone 90 between the sidewall 92 of housing 60, where the gases flow downwardly in a manner, whereby additional heat is transferred from the products of combustion to coil 30. As noted above, the exterior portion of housing 60 is supplied with a covering 62 of thermally insulating material which minimizes loss of heat through housing 60 to the atmosphere and thus makes more heat available for transfer to the water flowing in coil 30.

The relatively cool products of combustion flow from zone 90 along the base portion 96 of housing 60 through an opening in the housing (not shown) adjacent rear wall 18 of exterior housing 12. The gases flowing in base portion 96 are separated from the burner 32 by a plate 98 which isolates the hot combustion gases therein from the relatively cool gases being discharged. Rear wall 18 of housing 12 includes a flue deflector 100 adjacent an opening 102 and the exhaust gases from housing 60 flow around deflector 100 for final discharge through opening 102 to the atmosphere.

While coil 30 of the present embodiment has been illustrated without fins it is foreseen that the exterior surface thereof may be provided with fins to increase the heat transfer area available to receive heat by convection from the gases. In either case, moisture will tend to form on the coil from the condensation of the products passing along the cooler coil walls. The condensation forming on the interior surface of coil 30 enhances the overall heat transfer to the coils since the liquid is a good absorber of the infrared radiation and is quickly heated; this heat is then transferred by conduction through the tube walls to the water flowing therein. The moisture forming on the inside surfaces of coil 30 runs down this surface and is deposited on the upper face 106 of plate 98 which is sloped as seen in FIG. 3 to direct the liquid to an opening 108 therein, whereby the liquid is deposited in base 110 of housing 12. Similarly moisture forming on the exterior surfaces of coil 30 runs down these surfaces to base 110, which is also sloped, and which directs the liquid to drain 112 whereby it is discharged from the housing.

In operation the heater is adapted to function automatically when the pool pump is in operation and is provided with a conventional thermostat or aquastat (not shown) which senses inlet water temperature. If the water temperature is below the desired minimum temperature the fan or blower 76 is turned on by conventional control means and when it is up to speed, the electric gas valve and ignition system are actuated to start the burner and heat pool water flowing through valve 40 and coil 30. A flame proving system (not shown) is provided to detect ignition and shut down the burner on failure of the burner to ignite. In addition, a high-limit temperature switch in the outlet 34 of coil 28 may be provided to prevent overheating of the unit in the event of insufficient waterflow and a timer can be incroporated with blower 76 to cool the unit after the burner shuts off and thereby reduce lime buildup in the heat exchanger.

Another embodiment of the swimming pool heater of the present invention is illustrated in FIGS. 5-9, and more specifically, in FIGS. 5 and 6 there is shown a generally rectangular swimming pool heater having an outer decorative housing 152 including front and rear wall panels 154 and 156 respectively. The function and operation of the heater of this embodiment is somewhat similar to the previously described heater and, accordingly, numerals applied to the elements of the prior embodiment are utilized below to indicate like parts.

As in the prior embodiment rear wall 156 of housing 150 includes three openings 20, 21 and 22 through which the various water and gas lines extend for connection with the heater components therein. Water from the pool's filter system is supplied through opening 20 to inlet 24 of a manifold 160 and flows therefrom through the multiple tube heat exchanger 162 which extends between manifold 160 and manifold 164. The heat exchanger illustrated in FIG. 7 is a four pass type which utilizes two tubes 166 in each pass of the water flow from one manifold to the other; however, it is noted that one, or more than two tubes, may be used in each pass as desired. As illustrated, however, tubes 166 are arranged in pairs and there are four pairs 168, 169, 170 and 172 extending from rear manifold 160 to front manifold 164.

The ends of each of the tubes 166 are mounted in and suitably sealed to, their associated manifold. Manifold 164 includes a central wall member 176 which divides the manifold into two separate chambers 178 and 180, whereby chamber 178 connects the downstream end of the first pair of tubes 168 to the upstream end of the second pair 169, and chamber 180 connects the downstream end of pair 170 with the upstream end of pair 172.

Referring now to manifold 160, it is seen that this manifold includes an interior wall 182 which separates the manifold into two sections 184 and 186. Manifold section 184 provides a bypass passage for excess water bypassed from heat exchanger 162 by valve 40, in the manner discussed above with respect to heater 10, so that it is returned directly to the pool through outlet passage 36. Manifold section 186 provides intercommunication between the various tubes 166 and is provided with a pair of integral partition walls 190 which divides the section into chambers 192, 194 and 196. Water entering inlet opening 24 of manifold 160 communicates with chamber 192 through valve 40 and at most only the maximum desired flow rate enters chamber 192 through conduit 42. The water in chamber 192 is in direct communication with the inlet ends of the pair of heat exchange tubes 168 and flows through these tubes in the first pass across the heater to chamber 178 in manifold 164. The water is returned from chamber 178 on the second pass through conduit 169 to chamber 194 where it is in communication with the inlet ends of the third pair of tubes 170. At the end of the third pass, the water flows from chamber 180 through tubes 172 to chamber 196 where it is discharged through opening 198 into manifold section 184 and returned through outlet 36 to the pool.

Heat exchanger 162 is mounted in an intermediate portion of housing 150 directly below planar heating unit 210. Heater unit 210 includes a generally rectangular plenum chamber 212 which corresponds substantially in size to the heat exchanger 162. An apertured ceramic burner plate 214 is provided as the base of plenum 212 which corresponds substantially to the plates 68 previously described. As before, a combustible mixture of gas and air is supplied to plenum chamber 212 through duct 216 from blower 218 and a gas supply line 218. The air required for combustion is drawn by fan 218 through an opening 220 which is formed in front panel 154 and is provided with a deflector plate 222, thereby eliminating unsightly flues and ducts.

Burner plate 214 is provided with a plurality of venturilike apertures 220 having a generally cylindrical inlet throat port 78 and an expanding outlet portion 82 on its outer face 224 opposite the upper surfaces of tubes 166. As with burner plate 68, the combustion of gases in apertures 82 heats the outer surfaces of ceramic plate 214 to incandescence to produce substantial amounts of infrared radiation. Under certain conditions, it has been found that sixty (60) percent of the available energy supplied to the burner by the combustible flue mixture is converted into radiant energy. This energy is directed downwardly toward tubes 166 to heat the tubes and the water flowing therein. These tubes, as seen in FIGS. 8 and 9, are spaced from each other and are provided with radiating fins which are adapted to absorb additional heat by convection from the products of combustion formed as a result of the combustion in burner 214, which products are discharged downwardly upon and through the spacing between the tubes. it is noted that tubes 166 may be provided with other known types of surface extensions in lieu of fins in order to enhance heat transfer.

A plurality of generally inverted T-shaped deflectors 230 are mounted below tubes 166 downstream of the flow of products of combustion which deflects the hot gases around the bottom portion of the tubes to increase distribution of the gases and effect an increased and more uniform transfer of convective heat therefrom. ln addition, these deflectors 230 will reflect radiation which passes between the tubes 166 back toward the tubes to insure substantially full utilization of the radiation produced by burner 214. While deflectors 230 have been illustrated as T-shaped members, it is noted that other deflector shapes may also be utilized, and in particular it is foreseen that flat or curved plate members will provide satisfactory deflection of gases and reflection of radiation.

After the products of combustion pass between deflectors 230 they flow downwardly into discharge chamber 232 immediately below heat exchanger 162. Chamber 232 is thermally insulated at its sides and front by plates 234 to conserve heat and effect maximum heat transfer by convection to tubes 162. However, the rear portion of chamber 232 is open to permit the escape of the relatively cooled exhaust gases through an opening 236 having a deflector 238 in rear wall 156.

As in the prior embodiment, condensate will tend to form on the relatively cool tubes 166 as the hot gases pass through; this condensate falls from the tubes to the base 240 of housing which is sloped to direct the moisture to a drain 242 for discharge.

The operation of heater unit 150 is substantially the same as heater 10 previously discussed.

Although the illustrative embodiments of the invention have been described herein with reference to the accompanying drawings and for heating water for swimming pools, it is to be understood that the invention is not limited to that field of use or to the precise embodiment described herein, and that other fluids may be heated and that various changes and modifications may be effected therein by one skilled in the art without departing from the true scope or spirit of this invention.

We claim:

1. A fluid-heating device in the fluid flow path of a water circulation system comprising, a heat transfer conduit forming a portion of said fluid flow path, a gas burner associated with said conduit and adapted to supply heat to said conduit to heat the water flowing therein upon combustion of fuel in said burner, said burner being positioned centrally of said housing and said conduit providing a close packed heat transfer coil surrounding said burner, a generally airtight housing adapted to contain said conduit and said burner, said housing including an exhaust opening adapted to discharge products of combustion formed by said gas burner, wherein said coil and said housing cooperate to define a flow path in the housing for said products of combustion whereby said products of combustion first flow generally upwardly between said peripheral sidewalls and said coils and then downwardly between said coils and the walls of said housing prior to discharge through said exhaust opening whereby additional heat is provided to said coil by convection from said products of combustion.

2. A device as defined in claim 1 wherein said burner includes peripheral sidewalls adapted to produce radiant heat upon combustion of gases within the burner whereby said close packed heat transfer coil surrounding said burner receives radiant heat from said peripheral sidewalls.

3. A device as defined in claim 2 wherein said peripheral sidewall comprises, a plurality of burner plates having a plurality of orifices extending therethrough, each of said orifices including a throat portion of relatively small cross section extending from'an inlet at one surface of said plate and an expanding outlet portion extending from said throat portion to an opening at an opposite surface of the plate opposite said coil and having cross sections increasing from said throat portion to said opening.

4. A device as defined in claim 3 including, means for supplying a combustible air-gas mixture to said one surface of said plates for passage through said orifices at a mass flow rate such that the velocity of flow of the mixture through said throat portion of each orifice is greater than the velocity of flame propagation in the mixture and establishes a substantially laminar flow in said throat portion which projects a jet of said mixture centrally into said outlet portion with separation of said jet from the surface of said outlet portion, whereby to create a zone of turbulent low velocity recirculating flow between said jet and said surface of the outlet portion.

5. A device as defined in claim 1 wherein said housing is thermally insulated along the exterior thereof whereby a substantial portion of the heat from said products of combustion is transferred to said coils by convection and heat loss through said housing is avoided.

6. A device as defined in claim I wherein said housing includes a second opening through which condensate forming on said coils is discharged.

7. A fluid-heating device in the fluid flow path of a water circulation system comprising, a heat transfer conduit forming a portion of said fluid flow path, a gas burner associated with said conduit and adapted to supply heat to said conduit to heat the water flowing therein upon combustion of fuel in said burner, a generally airtight housing adapted to contain said conduit and said burner, said housing including an exhaust opening adapted to discharge products of combustion formed by said gas burner, said housing and said conduit cooperating to define a flow path in said housing for said products of combustion whereby additional heat is provided to said conduit by convection from said products of combustion, said burner being positioned adjacent the upper portion of said housing and including, a base member adapted to produce radiant heat upon combustion of gases within the burner, and said conduit including a plurality of heat transfer ducts operably interconnected for fluid communication therebetween, said ducts being located below said base member to receive radiant heat therefrom.

8. A device as defined in claim 7 wherein said heat transfer ducts comprise spaced finned members whereby the products of combustion from said burner flow between and around said ducts prior to discharge through said exhaust opening.

9. A device as defined in claim 8 including, a plurality of deflection plates mounted in said housing below said heat transfer ducts to deflect combustion products flowing between said ducts to effect substantially uniform convective heating of said ducts by said products of combustion.

10. A device as defined in claim 8 wherein said base member comprises, a burner plate having a plurality of orifices extending therethrough, each of said orifices including a throat portion of relatively small cross section extending from an inlet at one surface of said plate and an expanding outlet portion extending from said throat portion to an opening at an opposite surface of the plate opposite said coil and having cross sections increasing from said throat portion to said open- 11. A device as defined in claim 10 including, means for supplying a combustible air-gas mixture to said one surface of said plates for passage through said orifices at a mass flow rate such that the velocity of flow of the mixture through said throat portion of each orifice is greater than the velocity of flame propagation in the mixture and establishes a substantially laminar flow in said throat portion which projects ajet of said mixture centrally into said outlet portion with separation of said jet from the surface of said outlet portion, whereby to create a zone of turbulent low velocity recirculating flow between said jet and said surface of the outlet portion.

12. A fluid-heating device comprising, a substantially airtight housing, gas burner means in said housing for producing radiant heat therein positioned adjacent the upper portion of said housing, said gas burner means including a base member adapted to produce radiant heatupon combustion of gases within the burner, means defining a flow path for said fluid through said device adjacent said burner means whereby fluid is heated by said radiant heat, said means defining a fluid flow path including a plurality of heat transfer ducts operably interconnected for fluid communication therebetween, said ducts being located below said base member to receive radiant heat therefrom, said housing having an exhaust opening therein for the products of combustion formed in said burner and confining said product of combustion prior to discharge through said opening adjacent said flow path defining means to supply additional heat to said fluid by convection.

IS. A radiant fluid-heating device comprising, an annular insulated housing defining a generally cylindrical heating chamber, burner means mounted within the central portion of said chamber having an apertured peripheral sidewall adapted to produce radiant heat in said chamber upon combustion of gases adjacent said apertures, an annular closepacked coil within said housing surrounding said burner and receiving radiant heat therefrom said coil defining a first annular exhaust passage between said peripheral sidewall and said coil and a second annular exhaust passage between said coil and the walls of said housing, said exhaust passages being in airflow communication adjacent the top of said housing said heating chamber having an exhaust opening therein, whereby products of combustion from said burner flow upwardly in said first passage to said second passage wherein said gases flow downwardly adjacent said coils to said exhaust opening and supply additional heat by convection to said coils and the water flowing therein.

14. A device as defined in claim 13 for heating water for a swimming pool including, valve means operatively connected to said coils for supplying a predetermined volume flow of water to said coil and bypassing excess water back to the pool.

15 A radiant fluid-heating device comprising, an insulated housing defining a heating chamber therein, burner means mounted within said chamber adjacent the top of said housing and having an apertured substantially planar base portion adapted to produce radiant heat in said chamber upon combustion of gases adjacent said apertures, a plurality of generally elongated tubular heat transfer ducts mounted within said housing below said burner and receiving radiant heat therefrom, said heat transfer ducts being connected in liquid communication with each other to provide a flow path for said water and defining an exhaust chamber in the base of said housing, said exhaust chamber having an exhaust opening therein adapted to provide communication between said exhaust chamber and the atmosphere, whereby products of combustion from said burner flow downwardly through and around said heat transfer ducts to said exhaust chamber and said exhaust opening to supply additional heat by convection to said coils and the water flowing therein.

16. A device as defined in claim 15 for heating water for a swimming pool including, valve means operatively connected to said coil for supplying a predetermined volume flow of water to said coil and bypassing excess water back to the pool.

17. A device as defined in claim 15 including, a plurality of deflection plates mounted in said housing below said heat transfer ducts to deflect said products of combustion about said heat transfer ducts prior to discharge from said housing to effect substantially uniform convection heating of said ducts by said products of combustion and to reflect radiation passing between said ducts upwardly towards said ducts.

18. A system for heating swimming pool water wherein the water is circulated from and to the pool which includes a radiant heating device for the water which comprises, a substantially airtight housing, gas burner means in said housing for producing radiant heat therein, means defining a flow path for said fluid through said device adjacent said burner means whereby said fluid is heated by said radiant heat, said housing having an exhaust opening therein for products of combustion formed in said burner and confining said products of combustion prior to discharge through said opening adjacent said flow path defining means to supply additional heat to said fluid by convection, and means forming a bypass to divert water from flowing along said flow path which includes a slide valve member having a closed position in which all of the water flows along said flow path and which is movable from said closed position to permit a controlled portion of the water to flow through said bypass, said valve element being annular and concentrically positioned with respect to the stream of water entering said system and being slidable axially from said closed position thereby to open annular passageway to said bypass, and a coil spring surrounding said valve element and urging said valve element to said closed position, said spring having the characteristic that it holds said valve element in said closed position when the rate of waterflow along said heating path is below a predetermined level and it permits the water pressure to move said valve element from said closed position upon an elevation in the said flow.

19. Apparatus as described in claim 18 wherein said valve element has a waterflow passageway thereto of lesser diameter than the diameter of the stream of water flowing into said device.

20. A system as defined in claim 1 for heating water for a swimming pool including, valve means operatively connected to said coil for supplying a predetermined volume flow of water to said coil and bypassing excess water back to the pool.

21. A system as described in claim 20 including a bypass to divert water from flowing along said flow path and wherein said valve means comprises a slide valve member having a closed position in which all of the water flows along said flow path and which is movable from said closed position to permit a controlled portion of the water to flow through said bypass, said valve element being annular and concentrically positioned with respect to the stream of water entering said system and being slidable axially from said closed position thereby to open an annular passageway to said bypass, and a coil spring surrounding said valve element and urging said valve element to said closed position, said spring having the characteristic that it holds said valve element in said closed position when the rate of water flow along said heating path is below a predetermined level and it permits the water pressure to move said valve element from said closed position upon an elevation in the said flow rate. 

1. A fluid-heating device in the fluid flow path of a water circulation system comprising, a heat transfer conduit forming a portion of said fluid flow path, a gas burner associated with said conduit and adapted to supply heat to said conduit to heat the water flowing therein upon combustion of fuel in said burner, said burner being positioned centrally of said housing and said conduit providing a close packed heat transfer coil surrounding said burner, a generally airtight housing adapted to contain said conduit and said burner, said housing including an exhaust opening adapted to discharge products of combustion formed by said gas burner, wherein said coil and said housing cooperate to define a flow path in the housing for said products of combustion whereby said products of combustion first flow generally upwardly between said peripheral sidewalls and said coils and then downwardly between said coils and the walls of said housing prior to discharge through said exhaust opening whereby additional heat is provided to said coil by convection from said products of combustion.
 2. A device as defined in claim 1 wherein said burner includes peripheral sidewalls adapted to produce radiant heat upon combustion of gases within the burner whereby said close packed heat transfer coil surrounding said burner receives radiant heat from said peripheral sidewalls.
 3. A device as defined in claim 2 wherein said peripheral sidewall comprises, a plurality of burner plates having a plurality of orifices extending therethrough, each of said orifices including a throat portion of relatively small cross section extending from an inlet at one surface of said plate and an expanding outlet portion extending from said throat portion to an opening at an opposite surface of the plate opposite said coil and having cross sections increasing from said throat portion to said opening.
 4. A device as defined in claim 3 including, means for supplying a combustible air-gas mixture to said one surface of said plates for passage through said orifices at a mass flow rate such that the velocity of flow of the mixture through said throat portion of each orifice is greater than the velocity of flame propagation in the mixture and establishes a substantially laminar flow in said throat portion which projects a jet of said mixture centrally into said outlet portion with separation of said jet from the surface of said outlet portion, whereby to create a zone of turbulent low velocity recirculating flow between said jet and said surface of the outlet portion.
 5. A device as defined in claim 1 wherein said housing is thermally insulated along the exterior thereof whereby a substantial portion of the heat from said products of combustion is transferred to said coils by convection and heat loss through said housing is avoided.
 6. A device as defined in claim 1 wherein said housing includes a second opening through which condensate forming on said coils is discharged.
 7. A fluid-heating device in the fluid flow path of a water circulation system comprising, a heat transfer conduit forming a portion of said fluid flow path, a gas burner associated with said conduit and adapted to supply heat to said conduit to heat the water flowing therein upon combustion of fuel in said burner, a generally airtight housing adapted to contain said conduit and said burner, said housing including an exhaust opening adapted to discharge products of combustion formed by said gas burner, said housing and said conduit cooperating to define a flow path in said housing for said products of combustion whereby additional heat is provided to said conduit by convection from said products of combustion, said burner being positioned adjacent the upper portion of said housing and including, a base member adapted to produce radiant heat upon combustion of gases within the burner, and said conduit including a plurality of heat transfer ducts operably interconnected for fluid communication therebetween, said ducts being located below said base member to receive radiant heat therefrom.
 8. A device as defined in claim 7 wherein said heat transfer ducts comprise spaced finned members whereby the products of combustion from said burner flow between and around said ducts prior to discharge through said exhaust opening.
 9. A device as defined in claim 8 including, a plurality of deflection plates mounted in said housing below said heat transfer ducts to deflect combustion products flowing between said ducts to effect substantially uniform convective heating of said ducts by said products of combustion.
 10. A device as defined in claim 8 wherein said base member comprises, a burner plate having a plurality of orifices extending therethrough, each of said orifices including a throat portion of relatively small cross section extending from an inlet at one surface of said plate and an expanding outlet portion extending from said throat portion to an opening at an opposite surface of the plate opposite said coil and having cross sections increasing from said throat portion to said opening.
 11. A device as defined in claim 10 including, means for supplying a combustible air-gas mixture to said one surface of said plates for passage through said orifices at a mass flow rate such that the velocity of flow of the mixture through said throat portion of each orifice is greater than the velocity of flame propagation in the mixture and establishes a substantially laminar flow in said throat portion which projects a jet of said mixture centrally into said outlet portion with separation of said jet from the surface of said outlet portion, whereby to create a zone of turbulent low velocity recirculating flow between said jet and said surface of the outlet portion.
 12. A fluid-heating device comprising, a substantially airtight housing, gas burner means in said housing for producing radiant heat therein positioned adjacent the upper portion of said housing, said gas burner means including a base member adapted to produce radiant heat upon combustion of gases within the burner, means defining a flow path for said fluid through said device adjacent said burner means whereby fluid is heated by said radiant heat, said means defining a fluid flow path including a plurality of heat transfer ducts operably interconnected for fluid communication therebetween, said ducts being located below said base member to receive radiant heat therefrom, said housing having an exhaust opening therein for the products of combustion formed in said burner and confining said product of combustion prior to discharge through said opening adjacent said flow path defining means to supply additional heat to said fluid by convection.
 13. A radiant fluid-heating device comprising, an annular insulated housing defining a generally cylindrical heating chamber, burner means mounted within the central portion of said chamber having an apertured peripheral sidewall adapted to produce radiant heat in said chamber upon combustion of gases adjacent said apertures, an annular close-packed coil within said housing surrounding said burner and receiving radiant heat therefrom said coil defining a first annular exhaust passage between said periPheral sidewall and said coil and a second annular exhaust passage between said coil and the walls of said housing, said exhaust passages being in airflow communication adjacent the top of said housing said heating chamber having an exhaust opening therein, whereby products of combustion from said burner flow upwardly in said first passage to said second passage wherein said gases flow downwardly adjacent said coils to said exhaust opening and supply additional heat by convection to said coils and the water flowing therein.
 14. A device as defined in claim 13 for heating water for a swimming pool including, valve means operatively connected to said coils for supplying a predetermined volume flow of water to said coil and bypassing excess water back to the pool.
 15. A radiant fluid-heating device comprising, an insulated housing defining a heating chamber therein, burner means mounted within said chamber adjacent the top of said housing and having an apertured substantially planar base portion adapted to produce radiant heat in said chamber upon combustion of gases adjacent said apertures, a plurality of generally elongated tubular heat transfer ducts mounted within said housing below said burner and receiving radiant heat therefrom, said heat transfer ducts being connected in liquid communication with each other to provide a flow path for said water and defining an exhaust chamber in the base of said housing, said exhaust chamber having an exhaust opening therein adapted to provide communication between said exhaust chamber and the atmosphere, whereby products of combustion from said burner flow downwardly through and around said heat transfer ducts to said exhaust chamber and said exhaust opening to supply additional heat by convection to said coils and the water flowing therein.
 16. A device as defined in claim 15 for heating water for a swimming pool including, valve means operatively connected to said coil for supplying a predetermined volume flow of water to said coil and bypassing excess water back to the pool.
 17. A device as defined in claim 15 including, a plurality of deflection plates mounted in said housing below said heat transfer ducts to deflect said products of combustion about said heat transfer ducts prior to discharge from said housing to effect substantially uniform convection heating of said ducts by said products of combustion and to reflect radiation passing between said ducts upwardly towards said ducts.
 18. A system for heating swimming pool water wherein the water is circulated from and to the pool which includes a radiant heating device for the water which comprises, a substantially airtight housing, gas burner means in said housing for producing radiant heat therein, means defining a flow path for said fluid through said device adjacent said burner means whereby said fluid is heated by said radiant heat, said housing having an exhaust opening therein for products of combustion formed in said burner and confining said products of combustion prior to discharge through said opening adjacent said flow path defining means to supply additional heat to said fluid by convection, and means forming a bypass to divert water from flowing along said flow path which includes a slide valve member having a closed position in which all of the water flows along said flow path and which is movable from said closed position to permit a controlled portion of the water to flow through said bypass, said valve element being annular and concentrically positioned with respect to the stream of water entering said system and being slidable axially from said closed position thereby to open annular passageway to said bypass, and a coil spring surrounding said valve element and urging said valve element to said closed position, said spring having the characteristic that it holds said valve element in said closed position when the rate of waterflow along said heating path is below a predetermined level and it permits the water pressure to move said valve elEment from said closed position upon an elevation in the said flow.
 19. Apparatus as described in claim 18 wherein said valve element has a waterflow passageway thereto of lesser diameter than the diameter of the stream of water flowing into said device.
 20. A system as defined in claim 1 for heating water for a swimming pool including, valve means operatively connected to said coil for supplying a predetermined volume flow of water to said coil and bypassing excess water back to the pool.
 21. A system as described in claim 20 including a bypass to divert water from flowing along said flow path and wherein said valve means comprises a slide valve member having a closed position in which all of the water flows along said flow path and which is movable from said closed position to permit a controlled portion of the water to flow through said bypass, said valve element being annular and concentrically positioned with respect to the stream of water entering said system and being slidable axially from said closed position thereby to open an annular passageway to said bypass, and a coil spring surrounding said valve element and urging said valve element to said closed position, said spring having the characteristic that it holds said valve element in said closed position when the rate of water flow along said heating path is below a predetermined level and it permits the water pressure to move said valve element from said closed position upon an elevation in the said flow rate. 